The present invention is concerned with a novel seat belt assembly for use in vehicles, having rich energy absorbing property and by which the retracting amount by the retractor is increased, thereby promoting use of the retractor.
The seat belts have generally been employed to mitigate mechanical shocks to the passengers of vehicles such as automobiles and air craft resulting to provide safety performance. The seat belts of this sort were so far studied from various aspects and angles, and many proposals were so far presented.
In the early days, the belts were manufactured in two-point type to hold only the waist, but to attain more reliable safety performance, the belts were made in three-point type having an additional belt to hold the shoulder. In recent days there has been proposed the belts of the type in which the waist belt and the shoulder belt are made in a continuous form. The belt system of the aforesaid continuous type has an advantage that they need just only less retractor units than retractor units required by the aforesaid three-point belt system. The modern trend, however, has been placing increasing demand for the belts to provide more energy absorption, which has resulted in the use of shoulder belts having large absorption of energy. However, the belts of the aforesaid continuous type have to be made by joining together an ordinary belt and a belt having high energy absorption. Hence the joined place gives an uncomfortable touch feeling to the human body, and comes into contact with the guide members of the retractor when the belt is not being taken up along smooth retracting movement. It is, therefore, desired to make the belt with a single woven fabric without seams to improve the aforementioned defects. At present, however, to make such a belt is technically difficult and no satisfactory solution has been found.
In recent years, increased concern with regard to the improvement of retractors has resulted in the manufacture of retractors of various types. Such retractors, however, have all been design based on a prerequisite that the thickness of the belt is equal along the lengthwise direction, thereby imposing a limit to the amount of taking up the belt. To increase the take-up amount, the retractor must have increased volume, losing economy in space, particularly when it is used for the vehicles having narrow room. This is a fatal defect of the belt of the aforementioned continuous webbing type, losing the balance of whole parts of the vehicle. From such viewpoint, it is an important assignment to increase the take-up space just with using a retractor of an ordinary size.